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Aluminium
Aluminium (or aluminum; see spelling differences) is a chemical element in the boron group with symbol and atomic number 13. It is a silvery white, soft, nonmagnetic, ductile metal. Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth's crust. It makes up about 8% by weight of the Earth's solid surface. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. The chief ore of aluminium is bauxite. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates. Despite its prevalence in the environment, no known form of life uses aluminium salts metabolically. In keeping with its pervasiveness, aluminium is well tolerated by plants and animals. Owing to their prevalence, potential beneficial (or otherwise) biological roles of aluminium compounds are of continuing interest. Characteristics " storage facility in Stade Germany. The aluminium industry generates about 70 million tons of this waste annually.]] Physical Aluminium is a relatively soft, durable, lightweight, ductile and malleable metal with appearance ranging from silvery to dull gray, depending on the surface roughness. It is nonmagnetic and does not easily ignite. A fresh film of aluminium serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared radiation. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has about one-third the density and stiffness of steel. It is easily machined, cast, drawn and extruded. Aluminium atoms are arranged in a face-centered cubic (fcc) structure. Aluminium has a stacking-fault energy of approximately 200 mJ/m2. Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin and a critical magnetic field of about 100 gauss (10 milliteslas). Chemical Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is also often greatly reduced by aqueous salts, particularly in the presence of dissimilar metals. In highly acidic solutions aluminium reacts with water to form hydrogen, and in highly alkaline ones to form aluminates— protective passivation under these conditions is negligible. Also, chlorides such as common sodium chloride are well-known sources of corrosion of aluminium and are among the chief reasons that household plumbing is never made from this metal. However, owing to its resistance to corrosion generally, aluminium is one of the few metals that retain silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm (UV) and the 3,000–10,000 nm (far IR) regions; in the 400–700 nm visible range it is slightly outperformed by tin and silver and in the 700–3000 (near IR) by silver, gold, and copper. Aluminium is oxidized by water at temperatures below 280°C to produce hydrogen, aluminium hydroxide and heat: :2 Al + 6 → 2 Al(OH)3 + 3 H2 This conversion is of interest for the production of hydrogen. Challenges include circumventing the formed oxide layer, which inhibits the reaction and the expenses associated with the storage of energy by regeneration of the Al metal. Isotopes Aluminium has many known isotopes, whose mass numbers range from 21 to 42; however, only 27Al (stable isotope) and 26Al (radioactive isotope, t1⁄2 = 7.2×105 y) occur naturally. 27Al has a natural abundance above 99.9%. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10 has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 105 to 106 year time scales. Cosmogenic 26Al was first applied in studies of the Moon and meteorites. Meteoroid fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding drastically reduces 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago. Natural occurrence Stable aluminium is created when hydrogen fuses with magnesium either in large stars or in supernovae. In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon). Because of its strong affinity to oxygen, it is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes. Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. (2011) have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)4− to metallic aluminium by bacteria. It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al2O3, such as chromium or iron yield the gemstones ruby and sapphire, respectively. Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlO''x''(OH)3–2''x''). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions. Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica and the primary mining areas for the ore are in Australia, Brazil, China, India, Guinea, Indonesia, Jamaica, Russia and Suriname. Production and refinement minerals.]] Bauxite is converted to aluminium oxide (Al2O3) via the Bayer process. Relevant chemical equations are: :Al2O3 + 2 NaOH → 2 NaAlO2 + H2O :2 H2O + NaAlO2 → Al(OH)3 + NaOH The intermediate sodium aluminate, given the simplified formula NaAlO2, is soluble in strongly alkaline water, and the other components of the ore are not. Depending on the quality of the bauxite ore, twice as much waste ("red mud") is generated compared to the amount of alumina. The conversion of alumina to aluminium metal is achieved by the Hall-Héroult process. In this energy-intensive process, a solution of alumina in a molten ( ) mixture of cryolite (Na3AlF6) with calcium fluoride is electrolyzed to give the metal: : Al3+ + 3 e− → Al At the anode, oxygen is formed: : 2 O2− → O2 + 4 e− The aluminium metal then sinks to the bottom of the solution and is tapped off, usually cast into large blocks called aluminium billets for further processing. To some extent, the carbon anode is consumed by subsequent reaction with oxygen to form carbon dioxide. The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the process. The cathodes do erode, mainly due to electrochemical processes and metal movement. After five to ten years, depending on the current used in the electrolysis, a cell must be rebuilt because of cathode wear. Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy. The worldwide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters achieve approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the heat of reaction, 31 MJ/kg, and the Gibbs free energy of reaction, 29 MJ/kg.) Reduction line currents for older technologies are typically 100 to 200 kiloamperes; state-of-the-art smelters operate at about 350 kA. Trials have been reported with 500 kA cells. The Hall-Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoopes process. The process involves the electrolysis of molten aluminium with a sodium, barium and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%. Electric power represents about 20% to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the U.S. Aluminium producers tend to locate smelters in places where electric power is both plentiful and inexpensive—such as the United Arab Emirates with its large natural gas supplies, and Iceland and Norway with energy generated from renewable sources. The world's largest smelters of alumina are People's Republic of China, Russia, and Quebec and British Columbia in Canada. In 2005, the People's Republic of China was the top producer of aluminium with almost a one-fifth world share, followed by Russia, Canada, and the US, reports the British Geological Survey. Over the last 50 years, Australia has become the world's top producer of bauxite ore and a major producer and exporter of alumina (before being overtaken by China in 2007). Australia produced 77 million tonnes of bauxite in 2013. The Australian deposits have some refining problems, some being high in silica, but have the advantage of being shallow and relatively easy to mine. Recycling ]] Aluminium is theoretically 100% recyclable without any loss of its natural qualities. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in society (i.e. in cars, buildings, electronics etc.) is . Much of this is in more-developed countries ( per capita) rather than less-developed countries ( per capita). Knowing the per capita stocks and their approximate lifespans is important for planning recycling. Recovery of the metal via recycling has become an important use of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to the public awareness. Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide). An aluminium stack melter produces significantly less dross, with values reported below 1%. The dross can undergo a further process to extract aluminium. In Europe aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles. Recycled aluminium is known as secondary aluminium, but maintains the same physical properties as primary aluminium. Secondary aluminium is produced in a wide range of formats and is employed in 80% of alloy injections. Another important use is for extrusion. White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia), which spontaneously ignites on contact with air; contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste has found use as a filler in asphalt and concrete. recycling ton of could save the equivalent of a 999/160 cubic meter tank of gasoline, 329/200 tons of red mud, 143/100 tons of dust each year, 1,554 gallons of oil, 10 cubic yards of landfill space, 14,000 kWh of energy, 237,600,000 Btu’s of energy, 891/2 pounds of ozone each year, 4,383/1,000 tons of bauxite, 1,020 pounds of petroleum coke, 966 pounds of soda ash, 327 pounds of pitch, 238 pounds of limestone, 29/20 tons of , 81 pounds of air pollution, 789 pounds of solid waste, a 42 cubic meter lake, enough energy to power over 493/2,000 cars for a year, a CFL for 217/292 years, 71,280/19 homes for a year, enough oil to run the average car for 23,310 miles or circle the globe almost 1,740,480 times, 2,331/4 tons of green house gases, a 46,620,000 cubic meter lake, and 6,216 acres of soil from being polluted, 400 metric tons of , 14/39 metric tons of , 9,387/2,000 tons of biomass, 1,043/400 tons of , a 89,100/9,169 cubic meter container on propane, 97,047/4,000,000 tons of methane, 140/39 metric tons of , over 9,387/183,200 tons of smog, 10,323/10,000,000 tons of VOCs, 66,825/64 cubic meters of rain, 2,673/16,000 tons of particulates each year, 83,853/25 decibels of sound intensity, a 783/1,360 cubic meter container of biodiesel, 5,481/68,000 tons of glycerol, 149/458 tons of PETN, 999/8 pounds of , 171,500,000/9 metric tons of sulfuric acid, a 891/139 cubic meter tank of diesel fuel, 112/5 kilograms of nitric oxide, 333/50 tons of water vapor, 3,129/200 tons of , 30,303/2,000,000 tons of soot, 1,043/100 tons of 1,3-butadiene, 1,043/200 tons of butane, 29/22 pounds of sulfur hexafluoride, 3,339/1,000 tons of , 6,300/523 metric tons of trinitrotoluene, 7/10 pounds of , a 891/134 cubic meter container of kerosene, 112/39 metric tons of , 1,188/95 tons of methanol, 2,997/80 tons of sawdust, 29/123,200 pounds of octane, 7/11 grams of , 435/2 pounds of , 1,320 pounds of herbicides, 118,800/22,159 tons of , 2,871/452,200 tons of potassium hydroxide, 8,449/200,000 tons of , 119/500 tons of bleach/wood-ash, 119 pounds of calcium oxide, 2 pounds of , 12 tons of peat, 14/4,955 pounds of humic acid, 4 tons of ore, 2/5 ounces of , 28/25 gallons of biofuel, 1,584/5 pounds of , 7/9 metric tons of , 14/5 ounces of uranium ore, 500 metric tons of gypsum, 70/13 tons of , 6,300/59 tons of fertilizer, 594/35 tons of phosphate, 7/2 pounds of a year, 198/175 tons of pesticides, 58/46,935 pounds of , 252/5 pounds of , 8 tons of overburden, 19,800 tons of carrying capacity per hour, 280/17 metric tons of oil shale, 7/20 pounds of uranium oxide, 175,000/99 tons of mining waste, 224/3 pounds of bottom ash, 5,940/433 tons of wood fuel, 9,387/20 tons of carbon tetrachloride, 14/25 pounds of yellowcake, 49/80,000 pounds of , 60 pounds of , 49/16,000 pounds of , 14 tons of salt, 35/8 metric tons of , 280 tons of potassium chloride, 3,754,800/23 cubic feet of natural gas, 7/1,875 pounds of , 10,348/1,875 tons of copper ore, 1,120 pounds of , 3,113/62,500,000 tons of , 70,000/157 tons of coal dust, 33/2 kilograms of benzene, 99 tons of hydrogen peroxide, 1,314/15,625 pounds of , 9,506/89,755 milligrams of , 10 tons of , 28/9 tons of , 560 pounds of , 7/125 pounds of , 28/5 kilograms of , 28,161/16,000 tons of , 435/1,024 tons of iron oxide, 70,000/27 people, 133/55,000 grams of , 21/125 grams of diamonds, 7/400 grams of , 7/7,500,000 ounces of , a 63/250 cubic meter container of coal tar, 1,341/19 gallons of jet fuel, a 103,257/920 cubic meter container of sodium hypochlorite, 27,000 tons of , 297 pounds of chlorine monoxide, 2,376/149 tons of pellet fuel, 432,000 cubic feet of coal gas, 891/1,600 tons of ash/smoke each year, 3,911,250/2,977 metric tons of global warming, 3,960/323 tons of , 464/33,525 tons of bentonite, 21/610 kilograms of , 32 gallons of algae fuel, 200 pounds of haze, 15,750 tons of cyanide, 84,483/5,000,000 tons of formaldehyde, 2,376,000/199 tons of sand/gravel, 13,104/985 tons of acid rain, 1,120 bushels of charcoal, 21/10 metric tons of beryllium oxide, 178,200/199 tons of borax, 560/17 tons of gunmetal, 175/198 tons of rare earth elements, 700/117 tons of magnetite, 56/17 tons of castings, 420/23 tons of slag, a 2,373/50 cubic meter container of brine, 13,500 tons of potash, 27,000,000/209 tons of feldspar, 26/25 kilograms of , 371/5,000,000 pounds of flint, 891/3,200 tons of latex, 891/6,400 tons of chicle, a 9,387/66,868 cubic meter container of trichloroethylene, 7/5 metric tons of packaging, 864,801/250 gallons of sodium chlorite, 81/88,000 pounds of , 10,073/179,510 tons of carnotite, 476/375 tons of , 7,875,000,000/13 tons of food, 11,473/1,200 tons of carbonic acid, 14/113 tons of , 448/13 pounds of starch, 881/9,375 pounds of , 700/11 tons of brass, 237,600/217 tons of sandstone, 14 ounces of ammonium sulfate, 175/1,941 pounds of fluorite, 15/80,228 tons of land, 1,400 tons of product, a 9387 cubic meter tank of hydrogen fuel, 140/3 tons of bronze, 191,901,857/1,780,000,000 tons of , 4,752,000/152,073 tons of woodchips, 14,000/27 tons of alfalfa, 825 tons of ice a day, 140/43 metric tons of , a 22,275/2,309 cubic meter container of grease, 891/640 pounds of wax, 21/11,000 milligrams of , 7/800 micrograms of , 21/25,600 pounds of , 7/320 ounces of , 21/3,200 pounds of , 789/13 pounds of pigment, 789/1,280,000 pounds of coltan, 28/113 tons of , 143/25 tons of rockdust, 11,317/2,000 tons of resources, 8/5 tons of materials, 1,000/49 pounds of , 725 pounds of chloroform, 2,376/245 tons of acetone, 7,603,200/2,573 gallons of dye, 263/10 pounds of slate, 290/149 tons of hematite, 2,376,000/17 gallons of solution, 3,500/3 tons of concentrate, 1,099/10,000 milligrams of , 1,008/907 metric tons of pentane, 16/5 tons of residue, 128/5 kilograms of barium chloride, 84/5 metric tons of gunpowder, 40,000/99 tons of , 9/2 tons of aluminium ore, over 1,000 pounds of fuel, 297/56 tons of ethane, 700/9 tons of ethylene oxide, 1,188/199 tons of paraffin wax, 11,583/2,800 tons of ethylene, 160 tons of moisture, 91/7,920 metric tons of flue dust, 7 metric tons of , 700,000,000,000,000,000,000 metric tons of , 14/15 tons of potassium chlorate, 50,400/40,589 metric tons of toluene, 2,800/907 tons of sodium chlorate, 7/1,150 ounces of , 1,582/907 metric tons of sodium chloride, 400 tons of sea, 35/1,188 pounds of , 11,473/1,800,000 metric tons of MOX fuel, 28/15 tons of limonene, 224/5 tons of earth, 7/3 tons of , 1,400/423 metric tons of fiber, 20 kilograms of aluminium fluoride, 1,000 pounds of anode, 70 pounds of hydrogen fluoride, 4,455/4 tons of bats, 453,125/281 tons of chloromethane, 332,640,000,000/12,597 gallons of sewage, 11,583/16,000 tons of , 1 ton of , 100 grams of , 5/2 tons of aluminium oxide, 1,250 pounds of zinc oxide, 2,673/50,000 cubic meters of , 32,967/2,720,000,000 tons of dioxins, (1-4)/10 ounces of furan per hour, 560,000/17 worms, 371/2 grams (50 liters) of , 3,227/100 tons of baryte, 21/4,000,000 pounds of zinc cyanide, 3,227/40,000 tons of , 217/135 micrograms of , 56/5 tons of iron ore, 28/15 tons of , 567/1,250 tons of asbestos, 1,120/3 pounds of pulp, 105,600/139 tons of asphalt, 88,452/125 pounds of hydrochloric acid, 4,753/448,775,000,000 milliliters of , 65,772/125 pounds hydrofluoric acid, 22,275/2 silkworms, 22,275/4 primates, 65,975/3 milligrams of toxins, 4,200 tons of dirt, 400/11 pounds of , 21/2 pounds of mica, 700,000,000/3 cubic feet of flue gas, 34,300,000,000/1,377 tons of citric acid, 6,619,900,000/459 metric tons of calcium hydroxide, 1,400/243 gallons of bioethanol, 1,188/155 tons of tire-derived fuel, 3,754,800/3,671 gallons of avgas, 594/25 tons of refuse-derived fuel, 14/1,545 tons of protein, (554,400-316,800)/323 cubic meters of exhaust gas, a 147/1,220 ton meteorite, 1,188/4,975 pounds of gemstones, 224 pounds of lignin, 80 pounds of sugar, 7,000/3 cubic meters of biogas, 1,008,000 moles of hydrazine, over 111,375/2 butterflies, 59,400/19 gallons of alcohol, 14,900/229 tons of oil sands, 33,264,000,000,000/199 gallons of rocket propellant, a 4,455/284 cubic meter tank of methanol fuel, 1,188/125 tons of anthracite, a 81/10 cubic meter container of palm oil, 297/20 tons of lignite, 64 pounds of , 176,000/3 cubic yards of wood gas, 5,568,750 bees, 84/61 metric tons of butanol fuel, 56/1,425 pounds of , 875/9 grams of caprolactam, 297/25 pounds of acetaldehyde, 81/25 metric tons of glucose, 56/5 pounds of magnesite, 1/5 cubic miles of fog, 2,587/187,500,000 tons of , 389/31,250 pounds of , 84/5 tons of nitric acid, 6,167/4,6875,000 tons of chromium ore, 28 tons of lactic acid, 25,200/61 cubic meters of blau gas, 224/625 kilograms of , 56/505 tons of nitrocellulose, 168/25 tons of beeswax, a 2,673/640 cubic meter container of plant sap, 84/85 metric tons of autogas, 735,000,000/858,209 gallons of xylene, 41,720/23 gallons of whale oil, 50,400 sticks of dynamite, 217/50 pounds of corn oil, 891/6,800 tons of acetate, 112/13 pounds of , 3,129/1,000 tons of biochar, 2,376,000/1,187 gallons of naphtha, 47,520/23 gallons of coleman fuel, 5,400/257 tons of , 475,200/277 gallons of heating oil, 198/5 tons of freon, 63/112,250 grams of matter, 891/4 pounds of carnauba wax, 10/7 tons of plaster, 9,387/1,900 tons of pig iron, 50,660/229 gallons of petrochemicals, 28,161/3,485 acres of peanut oil, 1,043/300 tons of marsh gas, a 891/38 cubic meter container of coal oil, 2/9 gallons of hydraulic fluid, 2,673/128,000 tons of weeds, 990/19 tons of molasses, 391,125/458 gallons of lubricant, 1,188/(5-13) tons of zeolite, 70,000/113 gallons of renewable fuel, 162,000,000/257 cubic feet of pintsch gas, 6,125/3,504 tons of Pyrite, (1,782-2,673)/64 pounds of resin per year, (63-126)/590 tons of perchlorate, 66/49 tons of polyethylene, 84/5 kilograms of electrodes, 79,200,000/31 cubic feet of Blast furnace gas, 126/25 metric tons of malic acid, 252/85 metric tons of carbohydrate, 297/2 tons of , $3,105.60, gain almost 11,583/800 tons of per year, 2,673/160 tons of olives each year, 4,169 kwh of energy per year ---- recycling one metric ton of could save up to 8 metric tons of bauxite, 88/9 metric tons of , 4 metric tons of chemical products, 14,000 kwh of energy, over 10 metric tons of greenhouse gases, 12,950/229 gallons of oil, 51,800/229 acres of soil from being polluted, 2 metric tons of aluminium oxide, 35/2 kilograms of aluminium fluoride, 70,400/9 square meters of natural habitat potential, 88/27 metric tons of fossil fuels, 308/45 metric tons of shells, 44/27 metric tons of carbon monoxide, 10/3 metric tons of coal/ , 80/3 metric tons of ore/rock/soil/sand, 320/27 grams of nuclear fuel, 4/3,375 grams of , 176/401,625 metric tons of uranium hexafluoride, 88,000/2,781 metric tons of , a 55/9 cubic meter tank of aviation fuel, 5,000/207 tons of steam, 370/3 kilograms of tar, 968/675 metric tons of casting, 242/2,109,375 metric tons of phenol, 484/1,265,625 tons of bisphenol A, 1/750 grams of , 88/81 metric tons of clay, 8/243 kilograms of , 200/51 kilograms of , 16/3 plants each year, 4/16,875 grams of , 6,250/7 metric tons of , 2,054/75 metric tons of trona, 704/45 kilograms of solvents, 4/3 kilograms of , 296/3 kilograms of niobium pentoxide, 22,000/207 tons of , 1,100/837 metric tons of polytetrafluoroethylene, a 40/3 metric ton asteroid, 16/3 metric tons of volatiles/silicate, 800/27 kilograms of , 2,200/27 tons of PVC, 44/135 metric tons of nitrogen oxides, 484/27 pounds of vinyl chloride, 8/27 nanograms of , 96,008/9 square meters of ocean, 625 kilograms of toner, 32/3 metric tons of ingots, enough energy to power a 21/2 bedroom house for an entire year, and over 13,209/200,000 cars for a year, a CFL for 217/292 Years, one car to travel 194,250/229 miles, 777/2 power strips. Compounds Oxidation state +3 The vast majority of compounds, including all Al-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The coordination number of such compounds varies, but generally Al3+ is six-coordinate or tetracoordinate. Almost all compounds of aluminium(III) are colorless. Halides All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF3) features six-coordinate Al. The octahedral coordination environment for AlF3 is related to the compactness of fluoride ion, six of which can fit around the small Al3+ center. AlF3 sublimes (with cracking) at . With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral Al centers. These materials are prepared by treating aluminium metal with the halogen, although other methods exist. Acidification of the oxides or hydroxides affords hydrates. In aqueous solution, the halides often form mixtures, generally containing six-coordinate Al centers, which are feature both halide and aquo ligands. When aluminium and fluoride are together in aqueous solution, they readily form complex ions such as , , and . In the case of chloride, polyaluminium clusters are formed such as Al13O4(OH)24(H2O)127+. Oxide and hydroxides Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two oxide-hydroxides, AlO(OH), are boehmite and diaspore. There are three trihydroxides: bayerite, gibbsite, and nordstrandite, which differ in their crystalline structure (polymorphs). Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundum. These materials are of central importance to the production of aluminium and are themselves extremely useful. Carbide, nitride, and related materials Aluminium carbide (Al4C3) is made by heating a mixture of the elements above . The pale yellow crystals consist of tetrahedral aluminium centers. It reacts with water or dilute acids to give methane. The acetylide, Al2(C2)3, is made by passing acetylene over heated aluminium. Aluminium nitride (AlN) is the only nitride known for aluminium. Unlike the oxides it features tetrahedral Al centers. It can be made from the elements at . It is air-stable material with a usefully high thermal conductivity. Aluminium phosphide (AlP) is made similarly, and hydrolyses to give phosphine: : AlP + 3 H2O → Al(OH)3 + PH3 Organoaluminium compounds and related hydrides , a compound that features five-coordinate carbon.]] A variety of compounds of empirical formula AlR3 and AlR1.5Cl1.5 exist. These species usually feature tetrahedral Al centers, e.g. "trimethylaluminium" has the formula Al2(CH3)6 (see figure). With large organic groups, triorganoaluminium exist as three-coordinate monomers, such as triisobutylaluminium. Such compounds are widely used in industrial chemistry, despite the fact that they are often highly pyrophoric. Few analogues exist between organoaluminium and organoboron compounds except for large organic groups. The important aluminium hydride is lithium aluminium hydride (LiAlH4), which is used in as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichloride: : 4 LiH + AlCl3 → LiAlH4 + 3 LiCl Several useful derivatives of LiAlH4 are known, e.g. sodium bis(2-methoxyethoxy)dihydridoaluminate. The simplest hydride, aluminium hydride or alane, remains a laboratory curiosity. It is a polymer with the formula (AlH3)n'', in contrast to the corresponding boron hydride with the formula (BH3)2. Oxidation states +1 and +2 Although the great majority of aluminium compounds feature Al3+ centers, compounds with lower oxidation states are known and sometime of significance as precursors to the Al3+ species. Aluminium(I) AlF, AlCl and AlBr exist in the gaseous phase when the trihalide is heated with aluminium. The composition AlI is unstable at room temperature with respect to the triiodide: : 3 AlI → AlI3 + 2 Al A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al4I4(NEt3)4. Also of theoretical interest but only of fleeting existence are Al2O and Al2S. Al2O is made by heating the normal oxide, Al2O3, with silicon at in a vacuum. Such materials quickly disproportionates to the starting materials. Aluminium(II) Very simple Al(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example, aluminium monoxide, AlO, has been detected in the gas phase after explosion and in stellar absorption spectra. More thoroughly investigated are compounds of the formula R4Al2 which contain an Al-Al bond and where R is a large organic ligand. Analysis The presence of aluminium can be detected in qualitative analysis using aluminon. Applications General use Aluminium is the most widely used non-ferrous metal. Global production of aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal except iron (837.5 million tonnes). Forecast for 2012 is 42–45 million tonnes, driven by rising Chinese output. Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium. The main alloying agents are copper, zinc, magnesium, manganese, and silicon (e.g., duralumin) and the levels of these other metals are in the range of a few percent by weight. ]] (c. 1951)]] Some of the many uses for aluminium metal are in: * Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc. * Packaging (cans, foil, frame of etc.) * Construction (windows, doors, siding, building wire, etc.). * A wide range of household items, from cooking utensils to baseball bats, watches. * Street lighting poles, sailing ship masts, walking poles, etc. * Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment, MacBook Pro's casing * Electrical transmission lines for power distribution * MKM steel and Alnico magnets * Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs, and also in Wires/Cabling. * Heat sinks for electronic appliances such as transistors and CPUs. * Substrate material of metal-core copper clad laminates used in high brightness LED lighting. * Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite. * Aluminium can be reacted with hydrochloric acid or with sodium hydroxide to produce hydrogen gas. * Aluminium is used to make Food Containers, because of its characteristic - resistant to corrosion. * Aluminium with Magnesium alloy is used to make body of Aircraft. * Aluminium with other metals, used to make Railway tracks. * Aluminium is used to make Cooking Utensils, because it is resistant to corrosion, and light-weight. * A variety of countries, including France, Italy, Poland, Finland, Romania, Israel, and the former Yugoslavia, have issued coins struck in aluminium or aluminium-copper alloys. * Some guitar models sport aluminium diamond plates on the surface of the instruments, usually either chrome or black. Kramer Guitars and Travis Bean are both known for having produced guitars with necks made of aluminium, which gives the instrument a very distinct sound. Aluminium is usually alloyed – it is used as pure metal only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapor deposition or (very infrequently) chemical vapor deposition or other chemical means to form optical coatings and mirrors. Aluminium compounds Because aluminium is abundant and most of its derivatives exhibit low toxicity, the compounds of aluminium enjoy wide and sometimes large-scale applications. Alumina Aluminium oxide (Al2O3) and the associated oxy-hydroxides and trihydroxides are produced or extracted from minerals on a large scale. The great majority of this material is converted to metallic aluminium. In 2013 about 10% of the domestic shipments in the Unitated States were used for other applications. A major use is as an absorbent. For example, alumina removes water from hydrocarbons, which enables subsequent processes that are poisoned by moisture. Aluminium oxides are common catalysts for industrial processes, e.g. the Claus process for converting hydrogen sulfide to sulfur in refineries and for the alkylation of amines. Many industrial catalysts are "supported", meaning generally that an expensive catalyst (e.g., platinum) is dispersed over a high surface area material such as alumina. Being a very hard material (Mohs hardness 9), alumina is widely used as an abrasive and the production of applications that exploit its inertness, e.g., in high pressure sodium lamps. Sulfates Several sulfates of aluminium find applications. Aluminium sulfate (Al2(SO4)3·(H2O)18) is produced on the annual scale of several billions of kilograms. About half of the production is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordant, in fire extinguisher, as a food additive, in fireproofing, and in leather tanning. Aluminium ammonium sulfate, which is also called ammonium alum, (NH4)Al(SO4)2·12H2O, is used as a mordant and in leather tanning. Aluminium potassium sulfate (Al(K)(SO4)2)·(H2O)12 is used similarly. The consumption of both alums is declining. Chlorides Aluminium chloride (AlCl3) is used in petroleum refining and in the production of synthetic rubber and polymers. Although it has a similar name, aluminium chlorohydrate has fewer and very different applications, e.g. as a hardening agent and an antiperspirant. It is an intermediate in the production of aluminium metal. Niche compounds Given the scale of aluminium compounds, a small scale application could still involve thousands of tonnes. One of the many compounds used at this intermediate level include aluminium acetate, a salt used in solution as an astringent. Aluminium borate (Al2O3·B2O3) is used in the production of glass and ceramics. Aluminium fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic. Aluminium phosphate (AlPO4) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement. Aluminium hydroxide (Al(OH)3) is used as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics. Lithium aluminium hydride is a powerful reducing agent used in organic chemistry. Organoaluminiums are used as Lewis acids and cocatalysts. For example, methylaluminoxane is a cocatalyst for Ziegler-Natta olefin polymerization to produce vinyl polymers such as polyethene. Aluminium alloys in structural applications ]] Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). The strength and durability of aluminium alloys vary widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processes. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation. One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure eventually occurs, under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life. Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, melts without first glowing red. Forming operations where a blow torch is used therefore require some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling—in effect annealing the stresses. The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region. Another alloy of some value is aluminium bronze (Cu-Al alloy). History in Piccadilly Circus, London, was made in 1893 and is one of the first statues cast in aluminium.]] Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761, Guyton de Morveau suggested calling the base alum ''alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first termed alumium and later aluminum (see etymology section, below). The metal was first produced in 1825 in an impure form by Danish physicist and chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride with potassium amalgam, yielding a lump of metal looking similar to tin. Friedrich Wöhler was aware of these experiments and cited them, but after redoing the experiments of Ørsted he concluded that this metal was pure potassium. He conducted a similar experiment in 1827 by mixing anhydrous aluminium chloride with potassium and yielded aluminium. Wöhler is generally credited with isolating aluminium (Latin alumen, alum). Further, Pierre Berthier discovered aluminium in bauxite ore. Henri Etienne Sainte-Claire Deville improved Wöhler's method in 1846. As described in his 1859 book, aluminium trichloride could be reduced by sodium, which was more convenient and less expensive than potassium used by Wöhler. In the mid 1880s, aluminium metal was exceedingly difficult to produce, which made pure aluminium more valuable than gold. So celebrated was the metal that bars of aluminium were exhibited at the Exposition Universelle of 1855. Napoleon III of France is reputed to held a banquet where the most honored guests were given aluminium utensils, while the others made do with gold. Aluminium was selected as the material to use for the capstone of the Washington Monument in 1884, a time when one ounce (30 grams) cost the daily wage of a common worker on the project (in 1884 about $1 for 10 hours of labor; today, a construction worker in the US working on such a project might earn $25-$35 per hour and therefore around $300 in an equivalent single 10-hour day). The capstone, which was set in place on 6 December 1884, in an elaborate dedication ceremony, was the largest single piece of aluminium cast at the time. The Cowles companies supplied aluminium alloy in quantity in the United States and England using smelters like the furnace of Carl Wilhelm Siemens by 1886. Hall-Heroult process: availability of cheap aluminium metal Charles Martin Hall of Ohio in the U.S. and Paul Héroult of France independently developed the Hall-Héroult electrolytic process that facilitated large-scale production of metallic aluminium. This process remains in use today. In 1888 with the financial backing of Alfred E. Hunt, the Pittsburgh Reduction Company started, today it is known as Alcoa. Héroult's process was in production by 1889 in Switzerland at Aluminium Industrie, now Alcan, and at British Aluminium, now Luxfer Group and Alcoa, by 1896 in Scotland. By 1895, the metal was being used as a building material as far away as Sydney, Australia in the dome of the Chief Secretary's Building. With the explosive expansion of the airplane industry during World War I (1914-1917), major governments demanded large shipments of aluminium for light, strong airframes. They often subsidized factories and the necessary electrical supply systems.Mats Ingulstad, “‘We Want Aluminum, No Excuses’: Business-Government Relations in the American Aluminum Industry, 1917–1957,” in From Warfare to Welfare: Business-Government Relations in the Aluminium Industry, ed. Mats Ingulstad and Hans Otto Frøland, 33–68. (Oslo: Tapir Academic Press, 2012.) Many navies have used an aluminium superstructure for their vessels; the 1975 fire aboard [[USS Belknap (CG-26)|USS Belknap]] that gutted her aluminium superstructure, as well as observation of battle damage to British ships during the Falklands War, led to many navies switching to all steel superstructures. Aluminium wire was once widely used for domestic electrical wiring. Owing to corrosion-induced failures, a number of fires resulted. Etymology Two variants of the metal's name are in current use, aluminium ( ) and aluminum ( )—besides the obsolete alumium. The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990 but, three years later, recognized aluminum as an acceptable variant. Hence their periodic table includes both.IUPAC Periodic Table of the Elements. iupac.org IUPAC internal publications use either spelling in nearly the same number.IUPAC Web site publication search for 'aluminum'. Most countries use the spelling aluminium. In the United States and Canada, the spelling aluminum predominates.Bremner, John Words on Words: A Dictionary for Writers and Others Who Care about Words, pp. 22–23. ISBN 0-231-04493-3. The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium. In 1926, the American Chemical Society officially decided to use aluminum in its publications; American dictionaries typically label the spelling aluminium as "chiefly British". The various names all derive from its status as a base of alum. It is borrowed from Old French; its ultimate source, alumen, in turn is a Latin word that literally means "bitter salt". The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is alumium, which British chemist and inventor Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral alumina. The citation is from the journal Philosophical Transactions of the Royal Society of London: "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium.""alumium", Oxford English Dictionary. Ed. J.A. Simpson and E.S.C. Weiner, second edition Oxford: Clarendon Press, 1989. OED Online Oxford University Press. Accessed 29 October 2006. Citation is listed as "1808 SIR H. DAVY in Phil. Trans. XCVIII. 353". The ellipsis in the quotation is as it appears in the OED citation. Davy settled on aluminum by the time he published his 1812 book Chemical Philosophy: "This substance appears to contain a peculiar metal, but as yet Aluminum has not been obtained in a perfectly free state, though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of alumina." But the same year, an anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy's book, objected to aluminum and proposed the name aluminium, "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound." The ''-ium'' suffix conformed to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and strontium (all of which Davy isolated himself). Nevertheless, ''-um'' spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the 16th century, molybdenum, discovered in 1778, and tantalum, discovered in 1802. The ''-um'' suffix is consistent with the universal spelling alumina for the oxide (as opposed to aluminia), as lanthana is the oxide of lanthanum, and magnesia, ceria, and thoria are the oxides of magnesium, cerium, and thorium respectively. The aluminum spelling is used in the Webster's Dictionary of 1828. In his advertising handbill for his new electrolytic method of producing the metal in 1892, Charles Martin Hall used the ''-um'' spelling, despite his constant use of the ''-ium'' spelling in all the patents he filed between 1886 and 1903. Hall's domination of production of the metal ensured that aluminum became the standard English spelling in North America. Health concerns through five major routes: (1) paracellular; (2) transcellular; (3) active transport; (4) channels; (5) adsorptive or receptor-mediated endocytosis.]] Despite its widespread occurrence in nature, aluminium has no known function in biology. Aluminium salts are remarkably nontoxic, aluminium sulfate having an LD50 of 6207 mg/kg (oral, mouse), which corresponds to 500 grams for an person. The extremely low acute toxicity notwithstanding, the health effects of aluminium are of interest in view of the widespread occurrence of the element in the environment and in commerce. Some toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardation. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood–brain barrier. A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminium, such as antiperspirants and antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in amounts greater than 40 mg/day per kg of body mass. Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in general, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levels. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption, and maltol has been shown to increase the accumulation of aluminium in nervous and osseus tissue. Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. The estrogen-like effects of these salts have led to their classification as a metalloestrogen. The effects of aluminium in antiperspirants have been examined over the course of decades with little evidence of skin irritation. Nonetheless, its occurrence in antiperspirants, dyes (such as aluminium lake), and food additives has caused concern. Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults,Gitelman, H. J. "Physiology of Aluminum in Man", in Aluminum and Health, CRC Press, 1988, ISBN 0-8247-8026-4, p. 90 some studies point to risks associated with increased exposure to the metal. Aluminium in food may be absorbed more than aluminium from water. It is classified as a non-carcinogen by the US Department of Health and Human Services. In case of suspected sudden intake of a large amount of aluminium, deferoxamine mesylate may be given to help eliminate it from the body by chelation.Aluminum Toxicity from NYU Langone Medical Center. Last reviewed November 2012 by Igor Puzanov, MD Alzheimer's disease Aluminium has controversially been implicated as a factor in Alzheimer's disease. The Camelford water pollution incident involved a number of people consuming aluminium sulfate. Investigations of the long-term health effects are still ongoing, but elevated brain aluminium concentrations have been found in post-mortem examinations of victims, and further research to determine if there is a link with cerebral amyloid angiopathy has been commissioned. According to the Alzheimer's Society, the medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer's disease.Aluminium and Alzheimer's disease, The Alzheimer's Society. Retrieved 30 January 2009. Nevertheless, some studies, such as those on the PAQUID cohort, cite aluminium exposure as a risk factor for Alzheimer's disease. Some brain plaques have been found to contain increased levels of the metal. Research in this area has been inconclusive; aluminium accumulation may be a consequence of the disease rather than a causal agent. Effect on plants Aluminium is primary among the factors that reduce plant growth on acid soils. Although it is generally harmless to plant growth in pH-neutral soils, the concentration in acid soils of toxic Al3+ cations increases and disturbs root growth and function. Most acid soils are saturated with aluminium rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminium compounds. This concept of "corrected lime potential" to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement" of soils.Applying lime to soils reduces the Aluminum toxicity to plants. Wheat's adaptation to allow aluminium tolerance is such that the aluminium induces a release of organic compounds that bind to the harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. It was shown that sorghum's aluminium tolerance is controlled by a single gene, as for wheat. This is not the case in all plants. Biodegradation A Spanish scientific report from 2001 claimed that the fungus Geotrichum candidum consumes the aluminium in compact discs. However, other reports on it always refer back to the 2001 Spanish report and there is no supporting original research since that report. Better documented, the bacterium Pseudomonas aeruginosa and the fungus Cladosporium resinae are commonly detected in aircraft fuel tanks using kerosene-based fuels (not AV gas), and can degrade aluminium in cultures. However, this is not a matter of the bacteria or fungi directly attacking or consuming the aluminium, but rather a result of the microbes' waste having a corrosive nature. See also * Aluminium: The Thirteenth Element * Aluminium–air battery * Aluminium alloy * Aluminium foil * Aluminium granules * Aluminium hydroxide * Beverage can * Institute for the History of Aluminium * Panel edge staining * The Aluminum Association * Quantum clock * List of countries by aluminium production References External links * Aluminium at The Periodic Table of Videos (University of Nottingham) * CDC - NIOSH Pocket Guide to Chemical Hazards - Aluminum * Electrolytic production * World production of primary aluminium, by country * Price history of aluminum, according to the IMF * History of Aluminium – from the website of the International Aluminium Institute * Emedicine – Aluminium * * *